Funds are requested in this application to support, in part, the convening of the Fifth Ir Gene Workshop entitled "Immune Response Genes and Gene Products: Genetics, Molecular Biology and Function" to be held in St. Louis, MO in September 1982. This series of workshops, which began in 1974, was designed to foster information exchange and interactions among investigators studying immunological phenomena controlled by genes of the I-region of the major histocompatibility gene complex. These phenomena include: (1) genetically controlled responsiveness to antigens (Ir genes); (2) stimulation of mixed lymphocyte reactions; (3) regulation of cellular interactions; (4) encoding membrane glycoproteins (Ia) expressed by lymphocytes and macrophages; (5) control of specific helper and suppressor T cell factors; (6) resistance to viral oncogenesis; and (7) resistance and/or susceptibility to diseases in animals and men. This series of meetings continues to be the principal forum for rapid transfer of new information concerning I-region control of immunity. During the four years which will have elapsed since the last meeting, many new investigators have entered the field resulting in a virtual explosion of new information. The meeting organizers and investigators in this field who have been polled agree that a meeting in 1982 would be timely and appropriate. It would provide the opportunity to resolve issues that are currently in conflict, to focus upon issues to be investigated in the future and to compile the most recent work into a publication that should be useful to new workers and to those who would apply the results of these studies to other systems. Funds are requested to partially offset the travel expenses of 46 invited participants all of whom are major contributors to this field.